Libraries referencing models?

I have been perusing the source code for instiki (http:// www.instiki.org/show/HomePage) and noticed that in some of the library classes, there are references to model classes. And of course model classes refer to library classes.

When deployed in production mode, everything works, but if you deploy instiki in development mode, a superclass mismatch error occurs.

It strikes me that this tight coupling is a bad design: models should refer to libraries, but not vice versa. Otherwise, there is no separation of concern.